The present invention concerns an audio signal processing system in a television receiver or the like arranged to suppress the audible effects of transients produced when the system is energized or de-energized.
In an audio-frequency amplifier, sound is sometimes generated from a loudspeaker of the system when the system is energized and de-energized. Upon turn-on or turn-off of the TV receiver, the audio circuit may produce a very noticeable "pop" or "click" despite the absence of noise at its input because of rapid transitions of potentials within the amplifier or components coupled to the amplifier due to power supply transitions. If such a phenomenon occurs in a pre-amplifier, the aforesaid sound can be greatly amplified by the power amplifier. To eliminate this source of undesirable sound or noise, it is desirable to silence or mute the signal during these transient conditions. Accordingly, the audible effects of transients associated with energization and de-energization of the system are suppressed by apparatus arranged according to the present invention.